Articles such as food, cosmetics, and medicines, that contain oils and fats, suffer from oxidation or peroxidation of the oil and fat components caused by atmospheric oxygen, which is the most serious problem in storage, preservation, and processing of such articles. Unsaturated fatty acids contained in oils and fats, such as linoleic and linolenic acids, are known to be particularly prone to peroxidation by oxygen to generate lipid peroxides, free radicals, or even carcinogenic substances. Oxidation and peroxidation cause not only coloration, discoloration, denaturalizaton, abnormal odor, or decrease in effective nutritional value of the articles, but also generation of toxic substances, which results in deterioration of product quality.
In order to inhibit such oxidation and peroxidation of unsaturated fatty acids, and to prevent deterioration of product quality, various antioxidants have conventionally been used. Antioxidants act on peroxide radicals, which are generated in oxidation, to terminate chain oxidation, or alternatively act on free radicals to terminate oxidative reaction. Commonly used antioxidants are synthetic antioxidants, such as butylhydroxyanisol (BHA) and butylhydroxytoluene (BHT). Recently, however, safety of synthetic antioxidants has come to be questioned as their use expands, and consumers are presenting growing rejections, which results in decrease in their amount of use. Further, synthetic antioxidants are oil soluble, and thus are hard to use in aqueous solutions.
On the other hand, as natural antioxidants of high safety, natural vitamin E (α-tocopherol), vitamin C, and the like are known. However, these natural antioxidants are extremely fat- or water-soluble, so that their applications are limited. The natural antioxidants also have disadvantages in that their activity cannot be maintained stably for a prolonged period of time.
There is thus a strong demand for natural antioxidants having strong antioxidative activity, high water-solubility, and long-term stability in antioxidative activity.
Collagen and hyaluronic acid are known to have effects on moisture retaining property, softness, and elasticity of skin. Collagen constitutes 90% of dermis of skin and is distributed all over the dermis to give appropriate elasticity and strength to the skin. Hyaluronic acid is widely distributed over living organisms such as skin, synovial fluid, corpus vitreum, ligament, and the like, and contributes in skin to cell adhesion, cell protection, formation of skin tissues, retainment of tissue moisture, and maintenance of softness. Collagen and hyaluronic acid are known to be decomposed in vivo with enzymes called collagenase and hyaluronidase, respectively. It is said that, when these enzymes decompose collagen and hyaluronic acid to decrease their amounts, skin loses moisture and tension, and develops wrinkles and sagging, which are typical symptoms of skin ageing.
In expectation of anti-ageing and anti-wrinkle effects on skin, it is proposed to add substances that inhibit activities of these enzymes, to skin preparations for external use and various cosmetics, and various collagenase inhibitors and hyaluronidase inhibitors have been developed to date.
Recently, acerola fruit has come to be known as a vitamin C-rich plant, and has now been used in beverages and health foods around the world. The vitamin C-rich acerola fruit has also been in use in cosmetics for the expected antioxidative effect of vitamin C in the fruit extract (JP-2814094-B (JP-2-200610-A), JP-2000-212026-A, JP-2000-212027-A, and JP-2000-212032-A).
However, only the pulp of acerola fruit, which has a high vitamin C content, is used in cosmetics and food, and the seeds hardly find effective use and are mostly discarded. A cosmetic composition is recently proposed containing a steam distillate of plant seeds containing acerola seeds for improving skin feel (JP-2001-226218-A). Further effective use of acerola seeds is desired.
Incidentally, the constituting elements, effects, and the like of acerola seeds are hardly known yet.